Multiple Myeloma Presenting as Bilateral Posterior Optic Neuropathy

We report a case of bilateral posterior optic neuropathy as the presenting sign of multiple myeloma. A 72-year-old woman experienced bilateral progressive visual loss leading to blindness in 1 week without optic disc swelling. Brain and orbit magnetic resonance imaging revealed thickening of both intracranial optic nerves with abnormal sheath enhancement in post-contrast sequences. Systemic work-up detected a monoclonal band in blood and urine, and skeletal survey showed lytic lesions in the skull bones and multiple collapsed vertebrae. Bone marrow biopsy revealed atypical plasma cells. On the basis of these findings the diagnosis of multiple myeloma was made even though there was neither hypercalcemia nor renal failure. The mechanism of visual loss is a presumed infiltration of the intracranial optic nerves and the adjacent meningeal coverings.